Energy Is Chemistry's Challenge

Richard Eisenberg, the Tracy H.Harris Professor of Chemistry at the University of Rochester and editor-in-chief of the ACS journal Inorganic Chemistry, sent me an e-mail recently to bring to my attention a “Forum on Solar and Renewable Energy” in the journal. “I know that the challenge of carbon-free energy for sustainable development is high on your agenda,” Eisenberg wrote.

“The forum is meant to be a sampler of cutting-edge research in basic science relating to different aspects of solar energy conversion,” he continued. “I genuinely believe energy for sustainable development in a carbon-free way is one of this century’s ‘grand challenges’ and that chemistry will play a central role in meeting it successfully.”

The forum appeared in the Oct. 3 issue of Inorganic Chemistry, and I just picked up a copy of the journal to leaf through the papers, many of them by chemists I know well from my years as a C&EN reporter. Eisenberg and Daniel G. Nocera, the W. M. Keck Professor of Energy and professor of chemistry at Massachusetts Institute of Technology, write in the preface to the forum: “If we consider where the world stands today in terms of energy use and where it will be in 2050 assuming continued economic development, we are faced with a daunting challenge of where that energy will come from if our energy profile is to be more CO₂-neutral. … We need to look beyond something incremental because the additional energy needed is greater than the total of all of the energy currently produced.”

Eisenberg and Nocera review the maximum energy that could be obtained from biomass, wind, nuclear, and hydroelectric in that period—leaving aside any practical considerations—and conclude that the energy needed by 2050 “is simply not attainable from these much discussed sources: The global appetite for energy is simply too great.” The answer “to this dilemma over the long term must be solar energy.”

The eight articles that make up the forum run to more than 100 pages of the journal. They are not light reading. The principal authors of the papers that make up the forum are Thomas J. Meyer, University of North Carolina, Chapel Hill (“Chemical Approaches to Artificial Photosynthesis”), Thomas E. Mallouk, Pennsylvania State University (“Light-to-Chemical Energy Conversion in Lamellar Solids and Thin Films”), Michael Grätzel, Swiss Federal Institute of Technology, Lausanne (“Solar Energy Conversion by Dye-Sensitized Photovoltaic Cells”), Gerald J. Meyer, Johns Hopkins University (“Molecular Approaches to Solar Energy Conversion with Coordination Compounds Anchored to Semiconductor Surfaces”), Eisenberg (“Platinum Chromophore-Based Systems for Photoinduced Charge Separation: A Molecular Design Approach for Artificial Photosynthesis”), Nocera (“Molecular Chemistry of Consequence to Renewable Energy”), Arthur J. Nozik, National Renewable Energy Laboratory (“Exciton Multiplication and Relaxation Dynamics in Quantum Dots: Applications to Ultrahigh-Efficiency Solar Photon Conversion”), and Nathan S. Lewis, California Institute of Technology (“Chemical Control of Charge Transfer and Recombination at Semiconductor Photoelectrode Surfaces”).

All of the papers stress the scope of the energy challenge. Nocera writes: “Energy consumption is predicted to increase at least twofold, from our current burn rate of 12.8 [terrawatts] to 28–35 TW by 2050. A short-term response to this challenge is the use of methane and other petroleum-based fuels as hydrogen sources. However, external factors of economy, environment, and security dictate that this energy need be met by renewable and sustainable sources, with water emerging prominently as the primary carbon-neutral hydrogen source and light as the energy input. A response to this ‘grand challenge’ of chemistry, however, faces a daunting hurdle: large expanses of fundamental molecular science await discovery if the sun and water are to be used as an energy source.”

What I find fascinating and heartening about the forum in Inorganic Chemistry is the enthusiasm of the researchers and the sheer chemical ingenuity that is already being applied to this difficult problem. I don’t know whether we can obtain 15–22 TW of usable energy from the sun by 2050, but if we have any hope of meeting this challenge, it lies with chemistry. It is critical that these research efforts receive expanded support in the years to come.

Thanks for reading.